Process for producing plastic laminates from continuously fed bands

ABSTRACT

Process for producing plastic laminates with metal laminae especially for printed circuits, by formation of one or more packages arranged in piles, obtained from a multicomponent band continuously fed in and, simultaneously, both from bands of supporting material impregnated with plastic material and from one or two copper bands.

BACKGROUND OF THE INVENTION

The invention concerns the processes for producing plastic laminatesusing metal laminae.

Plastic laminates usually consist of sheets formed of a number of layersof plastic materials stably associated, generally by pressing, onsupports of paper, fabrics, fibreglass or other materials.

The plastic materials used may be of phenol, melamine, epoxy, polyester,silicon, fluoride or others.

To make printed circuits a metal lamina, especially one of copper, isglued onto one or both of their sides during the pressing process.

A pile is formed of packages all Virtually the same, each one comprisinga certain number of sheets impregnated with plastic materials and copperlaminae placed one on each side of the package.

A metal sheet, of stainless steel or some other type, is placed betweeneach package, and the pile so formed is put in a multiple-plate presswhich simultaneously provides heat and pressure.

At the end of each heat cycle, in which a temperature of 190° C. may bereached at pressures of up to 100 kg/cm² lasting over 100 minutesincluding a cooling stage to 70°-80° C., a compact and rigid product isobtained the single components of which are closely associated together.

Bearing in mind the many components needed, their nature and dimensions,formation of packages is a somewhat lengthy and complex process; thisraises their cost considerably especially in production of laminates forprinted circuits. Clearly the presses needed for this process arecomplex and of low output because of the many heating plates in them,because of the need to produce simultaneously both heat and pressure,with exact timing of these stages, and the need to create, byconduction, uniform temperatures in the various packages making up thepile of which, obviously, only those at each end of it are in contactwith the heating plates.

The presence of many plates in the press not only complicates itstructure but lengthens the time required for loading and unloadingpackages while preparation of short runs is made problematic becauserelatively more costly.

SUMMARY OF THE INVENTION

Subject of the invention is a process for production of plasticlaminates, aimed at simplifying and speeding up formation of packages,to enable use to be made of more compact and simpler presses and tofacilitate transmission of calories during the heating stage and ofrefrigerating units during cooling.

The package or packages in the pile are made from a multicomponent bandfed in continuously and simultaneously with bands of supporting materialimpregnated with plastic material and with one, or two, external metalbands of copper or some other suitable material.

One end of the multicomponent band is laid on a flat surface of themachine and, after a metal sheet has been put on top of it, said band isfolded at 180° and matched onto the second face of said sheet then,after another metal sheet has been placed on said band, a second fold at180° is made in the direction opposite to the first fold and matched upwith the second face of the second sheet, then after a third metal sheethas been placed, yet another fold is made at 180° in the directionopposite to the second fold, and so on according to the number ofpackages it is desired to form.

Each length of said multicomponent band lying between one sheet of metaland another therefore forms a package with all the components of saidpackage in their usual order. At the end of the process the laminatesobtained can of course be separated by cutting the multicomponent bandbetween one package and another.

Advantageously the heat is supplied by connecting two ends of the metalbands at the beginning and end of the package or pile of packages to asuitably high-powered generator of electricity.

In this way said bands act as electric resistances. Said heating systemcan naturally be associated to the usual method of heating packages bymeans of heating plates or in some other way. In this case the packagesare heated more quickly and thermal efficiency is improved.

The components in the multicomponent band, the support bands impregnatedwith plastic material and the metal bands, can be fed in off reels oroff other continuous feed methods. This invention clearly offers manyadvantages. Formation of packages to produce laminates is much quickerand more accurate, it being possible to mechanize the whole operationwith consequent saving of time, labour and costs.

Utilizing cold machines, presses or autoclaves is much more simple andsuch equipment may be of the most varied kind.

Heating is applied to each single package and a uniform temperature canbe quickly obtained. Continuity among the copper laminae comprised ineach package by such laminae being in band form also leads to aconsiderable reduction in cooling times.

Both heating and cooling are therefore more speedy as the spread ofcalories and of refrigeration units in each package is not hindered bythe presence of fibreglass or other supporting materials impregnatedwith plastic material, well known to be poor conductors of heat, in thepackages above and below such material, as happens with the processesnow in general use.

While present methods imply adoption of large multiple-plate presses tocontain running costs, with the process here described even very smallmachines can be used for short runs and this applies both to directheating, package by package, and to formation of packages by amulticomponent band already prepared both with the support componentsand with copper laminae.

In the case of combined types of heating--the conventional kind throughthe plates at the ends of the pile of packages and the direct kindthrough copper laminae--heating times are of course still furtherreduced and output thereby increased.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Present operation of a multi-plate press for simultaneousgeneration of heat and, pressure with packages to make printed circuitsusing present processes.

FIG. 2 Packages of laminates, made by the process subject of theinvention, arranged in a press.

FIG. 3 Detail of the illustration in FIG. 2.

FIG. 4 Packages of laminates, made by the process subject of theinvention,arranged inside an autoclave.

FIG. 5 How heat and cooling spread through packages of laminates made bythe process subject of the invention, associated to processes in use atpresent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The press 10 contains heating plates 11 between which the piles 16 ofpackages 12 are placed.

Components of said packages 12 are the sheets 13 of fibreglass fabricsimpregnated with epoxy resins and the copper laminae 14 at the ends.

Steel sheets 15 are placed between one package and the next.

As shown by the zigzag line 20, the calories in the heating stage andrefrigeration units in the subsequent cooling stage have to pass throughthe sheets 13 of fibreglass fabric which are known to be very poor heatconductors, or through other supporting materials of equal insulatingproperties.

Efficiency is therefore very low.

FIG. 2 gives a diagrammatic view of the process subject of theinvention.

Components of the packages to make laminates are obtained from the bands30, 31, 32 of fibreglass fabric and from copper bands 33, 34 fed incontinuously off the respective reels 40, 41, 42 and 43, 44. Said bands"compacted" by the pair of rollers 25 26 form the multi-component band45. The end 46 of said band 45 is placed on the plate 61 of the press 60and after laying a steel sheet 65 over it, said band 45 makes a fold 47at 180° matching up with the second face of said sheet 65.

After a second sheet 66 has been laid over it, said band makes a secondfold 48 at 180° in the opposite direction to the first and then matchesup with the second face of the last sheet 66.

A third fold 49 is then made at 180° in the direction opposite to thethe second fold, and so on until the second end 50 reaches up againstthe second plate 62 of the press. In this way a series of packages like51, 52, 53, 54 is formed joined by the various folds made at 180° like47-49. Then the lower end pairs 35, 36 of the copper bands 33, 34 andthe pairs at their upper ends 37, 38 are respectively connected toconductors 70, 71 of a generator 75 of electricity.

On closing the electric circuit all sections of said bands comprisedwithin said ends 35, 36, 37, 38 act as electric resistances thusbecoming heated themselves and heating the lengths of band 30-32 offibreglass fabric placed between said copper bands 33, 34.

The effect of the heat given off by said copper bands, as indicated bythe short arrows 21 in FIG. 3, and of simultaneous pressure generated bythe press, brings about the pressing process and desired production ofplastic laminates. The folds at points 47-49 and others between thevarious lengths of multicomponent band 45 folded one way and the other,like a serpentine, are then cut through for quick and easy production oflaminates for printed circuits. FIG. 4 shows an autoclave 80 insidewhich may be seen, in diagrammatic form, a complex 60 similar to that inthe press 60 already illustrated in FIG. 2.

In this figure, and in the next one 5, the various parts are marked withthe same numbers as those used for similar ones in FIGS. 2 and 3.

Here too the compound band 45 is used to produce packages like 51-53.

FIG. 5 shows a process, like that described in FIGS. 2 and 3, associatedto processes in use at present. The plates 85 and 86 in fact give offheat as indicated by the zigzag lines 20.

The various packages, such as 51-53, are therefore subjected to twosources of heat, one from said plates 85 and 86 and one generated by thelengths of copper band 33 34 between the ends 35-36, 37-38, combiningthe two effects to achieve greater efficiency.

As the above invention has been described and explained solely as anexample of its use which is not limited to this, and to show itsessential characteristics, numerous changes can be mar to it accordingto industrial, commercial and other requirements, and other systems andmeans can be included without thereby altering its sphere of operation.

It must therefore be understood that the application to patent comprisesany equivalent use of the concepts and any equivalent product executedand/or in operation in accordance with any one or more of thecharacteristics indicated in the following claims.

I claim:
 1. A process for producing plastic laminates for printedcircuits, comprising forming at least two packages each includinginternal supporting sheets impregnated with plastic material andexternal laminates composed of bands of copper that wind continuouslybetween one package and a next forming 180° bends in one direction andanother direction with interposition of at least one sheet of steel;applying heat generated by connected ends of the copper bands to agenerator of electrical current, said forming including making thepackages from a multi-composition band composed both of the bands ofsupporting material impregnated with plastic material and of the copperbands so as to produce a plastic laminate for a printed circuit.
 2. Aprocess as defined in claim 1, wherein said making includes laying oneend of the multi-composition band on a plate, laying thereafter a steelsheet on said end, and then bending the band at 180° after a secondsteel sheet has been laid, bending the band again at 180° in an oppositedirection to the first bending, continuing the laying and bending untila desired number of packages has been reached, applying heat andpressure so as to form the printed circuit; and separating the printedcircuit by cutting the multi-composition band that connects two adjacentprinted circuits.
 3. A process as defined in claim 1, wherein saidforming includes winding the bands of supporting material impregnatedwith plastic material and the copper bands off reels for various bandsrespectively.